1. Field of the Invention
The present invention relates to a liquid discharge head used for a printer, a video printer, and the like adopted as the output terminal of a copying machine, a facsimile equipment, a word processor, a host computer, and the like. The invention also relates to a method for manufacturing liquid discharge heads, and to a recording apparatus. More particularly, the invention relates to the liquid discharge head provided with the substrate having heat generating members (electrothermal converting elements) formed on it to generate thermal energy as the liquid discharge energy, and to discharge recording liquid (ink or the like) from the discharge ports (discharge openings) as flying droplets which are caused to adhere to a recording medium. The invention also relates to the recording apparatus using such head.
Here, the term xe2x80x9crecordingxe2x80x9d referred to in the specification hereof not only means the formation of meaningful images, such as characters and graphics, recorded on a recording medium, but also, means the formation of images, such as patterns, which do not present any particular meaning.
2. Related Background Art
Conventionally, the so-called ink jet recording method performs recording by use of a liquid discharge head is of non-impact type, which generates less noise, while making a highly densified printing possible at higher speeds. Besides, it is comparatively easy to maintain such recording method. There is also a good possibility that this method is executable maintenance-free. For such advantages and reasons as described above, the ink jet recording method has been widely adopted in recent years.
Of the ink jet recording methods, there has been known the bubble jet recording method, in which ink is caused to foam by the application of heat to discharge ink from the discharge ports (discharge openings), hence forming images on a recording medium with the adhesion of ink to it. For the recording apparatus that executes this bubble jet recording method, there are provided discharge ports (discharge openings) that discharge ink; liquid flow paths communicated with the discharge ports; heat generating members (electrothermal converting members or the like) that generate energy for causing ink in the liquid flow paths to be discharged as has been disclosed in the specification of U.S. Pat. No. 4,723,129. With a recording apparatus of the kind, it becomes possible to record high-quality images at higher speeds, with less noise as described above. At the same time, it is possible to arrange the discharge ports in higher density. Therefore, this kind of recording apparatus has an advantage, among many others, that images can be recorded in high resolution with a smaller apparatus, and images are easily obtainable in colors. As a result, the bubble jet recording method is utilized for office equipment, such as a printer, a copying machine, and facsimile equipment. Further, it is widely utilized for the industrial use, such as textile printing system, among others.
The general structure of the liquid discharge head used for a recording apparatus of this kind is to arrange the substrate having a plurality of liquid flow paths formed on it, and the other substrate having a plurality of heat generating members on it, hence enabling the groove formation surface and the arrangement surface of the heat generating members to be positioned to face each other and fix them in a laminated state. Each of the heat generating members is then allowed to fit with each of the liquid flow paths, respectively. Further, on the end faces of the substrates arranged in the laminated state, the discharge port plate (discharge port formation member) is fixed. Then, a plurality of discharge ports arranged for the discharge port plate are communicated with the leading end of the liquid flow paths, respectively.
Also, there is a case where the end face of the substrate is arranged integrally as one body so it may be drilled for the provision of the discharge ports without preparing the discharge port formation member separately.
In recent years, it has been required that a liquid discharge head of the kind should be able to print highly precise images at higher speeds. To meet such a requirement, the applicant hereof has proposed the structure that provides a movable member that controls bubbles in each of the liquid flow paths to guide bubbles to the discharge port side, as disclosed in Japanese Patent Application Laid-Open No. 6-31918. With the formation of this structure, it is anticipated that the discharge efficiency and the refilling characteristics are enhanced significantly.
Now, for the structure disclosed in the specification of the above mentioned Laid-Open Application, which has a movable member in each liquid flow path, it is extremely important to secure the close contact and the accuracy of the relative positions between a pair of substrates and each of the movable members, as well as the walls of the liquid flow paths. In other words, since the arrangement density of the liquid flow paths becomes very high in order to obtain highly precise images in recent years, the clearance obtainable for each of the movable members and the walls of liquid flow paths becomes smaller still, and in the worst case, the operation of the movable members may become imperfect if the positional precision is not good enough. Also, if the close contact and the accuracy of the relative positions are unfavorable, ink leakage may take place that stains the interior of the apparatus. As a result, there is a fear that such ink leakage even causes a short circuit between electric conductors in some cases. Also, the ink supply to the discharge ports may become insecure, which causes a shortage of ink to be discharged in some cases.
For the conventional structure described above, if the pair of substrates, the movable members, and the walls of the liquid flow paths are formed by different materials, there is a fear that the positional deviation takes place or the close contactness is affected due to the difference in the expansion coefficients of materials along with the temperature changes in operation that may cause the thermal expansion of the substrates and discharge port formation member even though the assembly is made with case in good precision when the head is manufactured.
For the head having the movable members in the liquid flow paths as described above, the warping and positional deviation of substrates, as brought about by the difference in the thermal expansion coefficient, may impede the normal operation of the movable members. Therefore, it is required for such a head to secure the higher positional precision than the conventional ink jet head, which is not provided with the movable members.
The inventors hereof, therefore, have devised the prevention of the defective operation of the movable members by reducing the difference in the thermal expansion coefficient of each of the members with the provision of the one and the same element to be contained in the movable members and the walls of the liquid flow paths, and the members that fix the movable members, as well as in the members that fix the walls of the liquid flow paths.
In this respect, meanwhile, there is the U.S. Patent of the Xerox application for such a technology as described above. However, in accordance with the Xerox application, the walls of liquid flow paths are provided by the performance of the anisotropic etching of the ceiling plate whose surface has the (100) plane of silicon crystal axes. However, with the structure thus disclosed, it is impossible to enhance the density of arrangement as required, because the section of each liquid flow path is made in the triangular form.
Further, if the silicon substrate whose surface has the (110) plane of crystal axes should be anisotropically etched, there is a problem that the resistance to ink of the walls of the liquid flow paths is lowered as compared with the (100) plane of the crystal axes, even if the section of each liquid flow path is formed square.
Therefore, it is an object of the present invention to provide a liquid discharge head capable of maintaining the higher quality printing and the stable discharges without causing any considerable changes in the flow path resistance, the close contactness between substrates, and the relative positional accuracy even if temperatures are changed along with the high speed printing or the like. It is also the object of the invention to provide a method for manufacturing such head, and a recording apparatus using it.
In order to achieve this objective, the present invention is characterized in the provision of a liquid discharge head which comprises a pair of substrates fixed in lamination; a plurality of liquid flow paths arranged on the bonded faces of the substrates, the leading end of the plural liquid flow paths being communicated with a plurality of discharge ports; a plurality of heat generating members arranged on at least one of the substrates corresponding to each of the liquid flow paths; and movable members each having in the liquid flow path the free end thereof on the discharge port side, and a region between each of the heat generating members and the movable members having liquid residing thereon. Then, bubbles are created by enabling thermal energy generated by the heat generating members to act upon the liquid, and controlled by the movable members to discharge liquid in the liquid flow paths from the discharge ports to the outside. For this liquid discharge head, the movable members, members becoming side walls of liquid flow paths, members supporting the movable members, and members supporting the walls of liquid flow paths are all formed by materials containing silicon, and at the same time, the side walls of liquid flow paths are provided by patterning the material containing silicon formed on the surface of one of the pair of substrates. In this manner, the thermal expansion coefficients of the substrates and the discharge ports are substantially made equal to prevent the close contactness between the respective members from being lowered, and also prevent the relative positions between them from being deviated.
Further, if the structure is arranged so that the pair of substrates are bonded by the surface activation bonding at the room temperature, it is possible to prevent the dipping of bonding agent into the liquid flow paths.
It is also preferable to use silicon nitride or some other inorganic material for the materials that contain silicon, because such material has excellent resistance to solvent.
The recording apparatus of the present invention is provided with a liquid discharge head which has either one of the structures described above.
Also, in order to achieve the above-mentioned objective, the method of the present invention for manufacturing a liquid discharge head, which is provided with a pair of substrates fixed in lamination; a plurality of liquid flow paths arranged on the bonded faces of the substrates, the leading end of the plural liquid flow paths being communicated with a plurality of discharge ports; a plurality of heat generating members arranged on at least one of the substrates corresponding to each of the liquid flow paths; and movable members each having in the liquid flow path the free end thereof on the discharge port side, and a region between each of the heat generating members and the movable members having liquid residing thereon, and then, bubbles are created by enabling thermal energy generated by the heat generating members to act upon the liquid, and controlled by the movable members to discharge liquid in the liquid flow paths from the discharge ports to the outside, comprises the steps of forming all of the movable members, members becoming side walls of liquid flow paths, members supporting the movable members, and members supporting the walls of liquid flow paths by materials containing silicon; and forming the flow path side walls simultaneously by patterning the material containing silicon formed on the surface of either one of the substrate as film subsequent to the formation of this film on it.
Further, the method for manufacturing a liquid discharge head comprises the step of providing movable members each having its free end in the discharge port side in each of the liquid flow paths, and also, a region where liquid resides between the movable member and each of the heat generating members. Here, the movable members are formed by material containing silicon, and also, the step in which the movable members are provided is the step of bonding the movable members at least to one of the paired substrates at the room temperature.